Combustion processes in the cylinders of a combustion engine result in the generation of thermal energy which warms regions adjacent to the combustion space, e.g. cylinder heads and cylinder liners. Such regions situated nearest to the combustion space, e.g. the lower part of the cylinder head, reach a higher temperature than those at a greater distance from the combustion space, e.g. the lower part of the cylinder liner. Warmer and cooler zones therefore occur in cylinder heads and cylinder liners during operation of a combustion engine. In operating situations where the engine is under heavy load for a lengthy period the warmer zones may reach very high temperatures.
Conventional cooling systems for cooling of combustion engines circulate coolant which may be at a temperature within the range 80-90° C. during normal operation. When the coolant circulates through the engine, cooling ducts provide all cooled zones in the engine with cooling by coolant at substantially the same temperature and flow. In operating situations where an engine is under heavy load, the cooling may become deficient in the warmest zones of the cylinder head and the cylinder liner. Other zones where there is less thermal load will be provided with cooling which may result in prolonged engine warm-up time after a cold start.
WO 2012/101014 refers to a cooling system with a circulating coolant for cooling a cylinder head of a combustion engine. The system has an inlet line which conveys the coolant initially to a central region of a lower cooling chamber in the cylinder head. This lower chamber has radial ducts which lead the coolant radially outwards. The coolant is received in an annular duct from which it passes upwards via an aperture to an upper cooling chamber in the cylinder head The coolant is thereafter led away from the cylinder head via an outlet duct.